Method for heat treatment



.Patented June 2,1931

UNITED" STATE-s CARL I. HAYES, OF PROVIDENCE, RHODE ISLAND` METnoD Fon. HEAT TREATMENT f Application ala may 25,

The present invention relates to a novel method for heat treating metals, andis a continuation in part of copending applica- .tion Serial No. 277,231,1iled May 12, 1928"l for electric furnace.

The novel `method lrelates broadly to the heat treatment of metals in an enveloping atmosphere of controlled constituency and to control of the metal during heat treat- I ment by providing a transparent, colorless,

gaseous curtain for, the heating chamber through which the heat treated metals may be readily inserted and removed, and

'through which the progress of the heat treatment` may be visually observed.

The invention may be carried out in various way, but for the purpose of the present disclosure one example of an vapparatus is shown in the accompanying drawings, in

.20 which:

Figure 1 is a front view of the electrically heated furnace showing one means by which gases may be introduced to form athin film or curtain across the entrance to the furnace chamber.

Figure 2 is a' central' sectional view on line 2--2 of Figure 1, showing one arrangement of electrical heating units and showing a slit. or slot in the lower wall of the chamber thru which curtain forming gases may be introduced: y

Figure 3 is a section on line 3 3 ofFigure 2 showing one arrangement of electrical heating units and a. slot in the lower wall of the chamber for introducing a thin lm of gases to form a curtain across the mouth of the work-receiving chamber.

Figure 4 lis a diagrammatic View illustrating lone arrangement of a group of heating units electrically connected together.

Heretofore,Y in the treatment of metals by heat, particularly when subjecting such metals to high temperatures, it has been dithcult to control the metal enveloping atmosphere Within the heating chamber so as to correspond to the metal undergoing the heat treatment. Thus, steels normally require an -inert or non-reactive atmosphere, in order to eliminate oxidation and the resultant scaling and pitting; high speed steels, how- 1929. serial Nb. 365,975..l

ever, may be hardened by heattreatment in an 'atmosphere containing a slight, definite, excess of carbon monoxide.v

for heat treatment which permits an accurate control of the metal` enveloping atmos- Applicant therefore provides a furnace 'i phere, and also facilitates heat treatment control by using a colorless, transparent, gaseous curtain through which the metal may be inserted and removed, and through .which the heat treating may be observed.

With reference 'to the drawings, the invention may be practiced by providinga furnace 10, supported on legs 11, which is built o f suitable refractory material and within which is formed a work-receiving chamber -12 which may be heated either by gas or electricity in any suitable wa'y; that herein shown being arranged to be heated by an electric current passing thru a group y of resistance bars. 13, in which group the circuit wires are connected to the terminal rods 14 and the current is controlled by a switch 15; the chamber 12 may therefore be heated to a high degree for hardening,

tempering, annealing or to any desired degree for otherwise treating metals by the applicationl of heat thereto.'

' It is preferred to 'use an electric heater for the furnace chalnber 12 because the heat main' can be better regulated and Vwill better tain constant temperatures.

The-essential feature of my present inven- I tioni's the provision of means for introduclng a `ilm of gases to form atransparent, ,colorless curtaln across the mouth or c ntrance of thefurnace chamber. which will seal vor v exclude atmospheric air from. the chamber 12 and will fill the chamber so as to produce the desired vatmospheric conditions therein one means of accomplishing this result is to form a narrow nozzle slot or ,opening 16 in the lower wall 17 of 'this chamber, the slot extending across the throat of the chamber` from side to rifle thereof, to

providey a relativelylong discharge 'et-or pipe 19-and an air introducing pipe 20 leadin g from' the blower-26. The openingsin these pipes are controlled andvaried to suit the conditions under which the furnace is operating.

When theair and gas is introduced thru these pipes 19and 20 to mix in the largerV combustion tube or chamber 18, the mixture is ignited thru the vent `hole 22 in the pipe 18. The products of combustion from in the chamber thus mixes with the curtain" Y i other than by'coin'busting gaseous fuel, such y as burning liquid or solid fuel to produce lthe gas thus ignited are thus forced under high pressure into the nozzle 16.

, These products spread 'throughout the length of the nozzle slot and are forced upwardly to form a thin ilm or sheet 23 across 'the throat 24 of the chamber 12, the pressure of these gases serving to exclude the outside air from the work receiving chamber ;v also-a portion of these gases when striking the opposite Wall .of the entrance opening flow into the -chamber 12 to fill the same. The continuous projection of additional gases maintains the' atmosphere-excluding sheet, and also maintains a continuous, regulated circulation of gases with the heating chamber. The oxygen which is first found within the furnace so as to produce different desired effects upon the work being treated. Also it is found that these atmospheric conditions Withinthe furnace'may be Varied Without appreciably affecting the temperature of the chamber, and that the provision of a transparent, colorless curtain permits a close-:visual supervision of the heat treatment. l v

Methodsv of forming the gaseous curtain the desired gaseous constituents, may obviously be used, as such variations in pro-l` cedure-are within the scope of the invention` as defined in the appended claims.

I-claim: 1. A method of heat treatingcomprising mixing combustible and oxygen bearing substances in predetermined proportions, combusting the mixture in a combustion chamber and utilizing the gaseous products of said combustion in aheat treating chamber as an enveloping atmosphere for the material to be heattreated.

2. A' method of heat treating comprising mixing combustible and oxygen bearing substances in predetermined proportions, combusting the mixture in a combustion chamber toobtain gaseous products containing carbon monoxide and utilizing saidgaseous products of combustion in a heat treating chamber as an enveloping atmosphere for the material to be heat treated.

3. A' method of visual inspection and control for heat-treatment of metals in a furnace having an opening therein, comprising mixing combustible gases and oxygen bearing gases in predetermined proportions, com.

busting said gases, and projecting said coinbusted gases as a transparent colorless ,c'urtain across said opening to exclude atmospheric air. y

4. A method of heat treating a metal in a furnace having an opening, comprising inixing combustible gases and oxygen bearing gases in predetermined proportions, comusting said gases, projecting said combusted gases as a transparent curtain across said opening to exclude. atmospheric air andV utilizing said combusted gases as an enveloping atmosphere Bfor material in` said furnace to be heat-treated. A

5. A method of heat treating a metal in furnace having an opening, comprising mixing combustible gases and oxygen bearing gases in predetermined proportions, coinbusting said gases to produce a resultant gas containin carbon monoxide, projecting said combustel gases as a transparent curtain across saidopening to exclude atmospheric air and utilizing said combusted gases as ,an enveloping atmosphere for material in lsaid. furnace to be heat-treated.

6. In a method o'f'heat treating, the Istepsv of combusting predetermined proportions of combustible and oxygen bearing substances in a combustion chamber to obtain products nos of combustion of predetermined constituency, utilizing the products of combustion 1n a heat treating chamber as an enveloping atmosphere for material to be heat treated,

and subjecting the material to be heat treated and the enveloping atmosphere Ato regulated heat. i y

7.',In a method of heat treating, the steps of combusting. predetermined vproportions,

Aof combustible and oxygen bearing p substances in a combustion chamber to obtain products-of combustion containing a prede- ,1 termined percentage of carbon monoxide,l utilizing the products of p combustion in'a heat treating chamber as an enveloping `atmosphere for material vto be heat treated,

and subjecting the material tov be heat treat ed and the enveloping atmosphere to regu--4 lated heat. Y

izo

8. A method of heat treating materialiii a furnace having an opening, comprisingV j mixin predetermined proportions vof combustib e gases and oxygen' bearing gases,

combusting the gases to produce products of combustion of predetermined constituency,

v utilizing part of said products of combustion as an enveloping atmosphere for material in said furnace to be heat treated, projecting part of said products of combustion as a transparent curtain across said opening to exclude atmospheric air, and sub]ecting the material to be heat treated and the enveloping atmosphere to regulated heat.

9. .A method of heat treating material in a furnace having an opening, comprising vmixin predetermined proportions of combustib e gases and oxygenbearing gases combusting the gases to produce products o l5 combustion containing CO and of predetermined constituency, utilizing part of said products of combustion as an venveloping atmosphere for material in said furnace to be heat treated; projecting part of said prodv ucts of combustion as a transparent curtain across said opening to exclude atmospheric air, and subjecting the material to be heat treated and the enveloping atmosphere l to regulated heat. t In testimony whereof I ax m si nature.

' CARL-I. ES.

DISCLAIMER '1,808,7'21.-Oarl I. Hag/es, Providence, R., I; METHOD FOR HEM` TREATMENT. n

Patent dated June 2, 1931. Disclaimer filed A ril 19 1938 b th i Harold O. Field; the patentee approving and` cclncurring. i y e assignee l Hereby enters this disclaimer of claims 1 and 6 of 'd L u,

[Qll Gazette May 24,. 1938-] sai e ers Patent,

so y 

